linux-kernel - Re: [PATCH] ELF core dump options

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Message-ID: <Pine.LNX.4.64.0707261753030.370@blonde.wat.veritas.com>
Date:	Thu, 26 Jul 2007 17:57:36 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Roland McGrath <roland@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	"Kawai, Hidehiro" <hidehiro.kawai.ez@...achi.com>
Subject: Re: [PATCH] ELF core dump options

On Thu, 26 Jul 2007, Roland McGrath wrote:
> 
> > hm, I'm now wondering whether testing i_nlink was the best (or official)
> > way of determining whether a MAP_SHARED vma is anonymous or file-backed.
> > Hugh will know.
> 
> Well, it doesn't exactly test that it's not "file-backed".  (Technically
> anything shared is file-backed, even if by a shmem virtual file.)  It tests
> whether the backing file will probably ever be found on disk later.  That
> gets shmem regions as well as originally-regular files that were deleted
> while mapped.  I think we asked around when this test was put it and it was
> deemed proper at the time.  (It doesn't really need to be a formal "what
> does the vm situation mean" guarantee, just a practical "you probably
> wanted that" test.)

Exactly, a rough heuristic which seemed to approximate what the coredump
people wanted when it went into 2.6.12.  No absolute justification to it.

Hugh
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